Blood pressure and plasma renin activity were studied in 13 infants of drug-dependent mothers (heroin and/or methadone) and 20 control newborns for a period of 21 days. Urinary excretion of epinephrine and norepinephrine were also measured at 24 and 48 h of age. The systolic blood pressure was found to be significantly elevated in newborns of drug-dependent mothers compared with controls (p less than 0.01), but diastolic blood pressure levels were similar. Plasma renin activity was significantly elevated (p less than 0.001) at 48-72 h and urinary epinephrine levels were significantly lower (p less than 0.05) at 24-48 h of age in the drug group, and norepinephrine levels were equivalent. Systolic hypertension and elevated plasma renin activity in these newborns of dependent mothers may be due to increased beta-adrenergic receptor sensitivity.